User's Manual

EMS Wireless Operator’s Manual
MirrorCell II CDM 812, CDM1912 Series
608112-1, Rev C
18
3.0 Installation Guidelines
3.1 Outdoor Site Selection
When the MirrorCell

II is used outdoors, site selection is one of the most critical
decisions affecting the overall performance of the repeater system. A repeater should
be located where it can receive a sufficient line of sight signal from the donor site to
maximize the repeater’s performance. For example, supposing a 1900 MHz MirrorCell

II has +39 dBm power output specification with a gain of 92 dB. Then, an input signal
level at the donor input connector (after the donor antenna and coax cable) of greater
than or equal to –53 dBm (composite power) is required for +39 dBm output: -53 dBm
+ 92 dB gain = +39 dBm.
Examples of repeater and accompanying antenna locations include, but are not limited
to:
 The roof of a building adjacent to the desired coverage area with the antennas
mounted to the penthouse or building sides
 The top of a hill that is obstructing the donor site’s coverage, with the antennas
pipe-mounted at ground level
 A water tower with antennas mounted at the top
 An existing utility pole, with equipment and antennas mounted below any existing
power lines
 A newly installed pole or tower
3.2 Donor and Server Antenna Selection
Proper selection of the repeater’s donor and server antennas is crucial in designing the
repeater system. The most important parameter to be concerned with is antenna
isolation. This is a measure of the ability of the donor and server antennas to avoid
receiving each other’s signals. Remember, the repeater is simultaneously transmitting
and receiving on each of the uplink and downlink frequency bands. For this to happen
successfully, the two antennas must be well isolated from each other, or excessive
signal levels from one antenna will be received by the other antenna. This sets up a
feedback loop, and oscillation begins. An example of this is shown in Figure 4 below: